Grinding machine



3 Sheets-Sheet 1 T W, F- M m Wm L G. my M Dec. 20, 1932. A. G. PLIMMERGRINDING MACHINE Filed April 4. 1952' a 1 null Dec. 20, 1932.

5 Sheets-Sheet 2 ALFRED GPUMMER (Minna/ Dec. 20, 1932 A. G. PLIMMERGRINDING MACHINE Filed April 4, 1932 3 Sheets-Sheet 5 Fig-10 r W 58 W5\0 --|o9 8; IS? 5? \aa 057 :52. 63 I 64) 1: 9 el I n so it: ALFRED G.PUMMER Patented Dec. 20, 1932 UNITED STATES PATENT OFFICE ALFRED G.PLIMMER, OF CINCINNATI, OHIO, ASSIGNOR TO CINCINNATI GBINDEBS vINCORPORATED, OI CINCINNATI,

GRINDING Application filed April 4,

This invention relates to improvements in machine tools and especiallyto improvements in grinding machines and to a feed control mechanism foruse therewith.

An object of the invention is the provision of an improved mechanism formodifying or stopping the feed between a tool and the Work when the workis reduced to a predetermined desired size.

Another object of the invention is the provision of an improvedelectrical sizing device having particular reference to grindingmachines and which will interrupt the feed between the grinding wheeland the work when the said wheel and work have approached one another apredetermined distance.

A further object of the invention is the provision of a sizin deviceadapted to stop the feed of the grinding wheel upon engagement thereofwith a mechanism positioned at a point representative of the final sizeof the work.

Other objects and advantages of the present invention should be readilyapparent by reference '0 the following specification con- OHIO, ACORPORATION OF OHIO MACHINE 1932. Serial No. 602,990.

Figure 7 is a fra entary sectional View taken on line 7 7 Figure 4.

Figure 8 is a sectional view taken on line 88 of Figure 1.

Figure 9 is a sectional view taken on line 99 of Figure 1.

Figure 10 is a sectional view taken on line 1010 of Figure 9.

Figure 11 is a diagrammatic view of one of the circuits employed withthe invention.

Figure 12 'is a diagrammatic view of another circuit which co-operateswith the circuit shown in Figure 11.

Figure 13 is a diagrammatic view of an electrical circuit showing amodification of the invention employing part of the circuits of Figures11 and 12.

Figure 14 is a semi-diagrammatical illustration showing the invention asused with a grinding machine of a different type from ,that shown inFigure 1.

Throughout the several views of the drawings similar referencecharacters are employed to denote the same or similar parts.

While this invention has application to vasidered in conjunction withthe accompanyrious types of machine tools in which a relaing drawings,forming a part thereof, and it tive feed between the tool and the workis is to be understood that anymodifications may had in order to reducethe work to the desired be made in the exact structural details theresize and the movement of one of which parts shown and described withinthe scope of the is stopped when the work is reduced to the appendedclaims without exceeding or deraid final or desired size, it has beenshown in parting from the spirit of the invention. the drawings inconnection with a grinding In the drawings: machine. The particulargrinding machine Figure 1 is a front elevation of a grinding illustratedin the drawings is what is known machine embodying the improvements ofcommercially as a plung cut grinder or inthis invention. feed type of agrinding machine in which a Figure 2 is a fragmentary sectional viewcontinuous feed is had of the grinding wheel showing the feed of thetool or grinding or work without relative traverse therebewheel and asseen particularly from line 22 tween during the grinding operation. Itis on Figure 1. I to be understood, however, that with few Figure 3 isan enlargeddetail view of parts modifications the invention may be usedwith of the feed mechanism as seen substantially the traverse type ofgrinding machine.

from line 33 on Figure 2. Accordingly, the machine shown in the Figure4.- is an enlarged elevational view drawings comprisesa bed 15 havingformed of the improved sizing device of this invenon the upper surfacethereof guideways 16 tion. for guiding the work supporting table 17 inFigure 5 is a top plan view of the parts its longitudinal movementsalong the bed.

shown in Figure 4. The table 17 has mounted thereon the ad]ust- Figure 6is a sectional View as seen from able head stock 18 and opposed tailstock 19 line 66 on Figure 4. from WlllCh respectively extends thecenters 20 and 21 for holding the work 22 therebetween. The head stock18 is ada ted to be wer driven which throu h the g 23 efects therotation of the wor while being supported by the centers and 21.

The bed 15 is provided on its rear surface with a projection or support24 having formed thereon guideways 25 for a grinding wheel carriage 26.The carriage 26 has journaled in bearings 27 a spindle 28 to one end ofwhich is secured a grinding wheel 29. Any suitable or desirable meansmay be provided for effecting the rotation of the s indle 28 andgrinding wheel 29 at the usual 'gh inding rate of speed. In order toreduce t e wor to the desired size, the carriage 26 and grinding wheel29 are adapted to be fed relative ,to the ways 25 toward the work 22.For this purpose the carriage has secured to it interiorly thereof thenut 30 threadedly engaged with an adjusting or cross feed screw 31ournaled in its outer end in a suitable bearing provided by the housing32. This housing 32 encloses a gear 33 keyed or otherwise secured to theendof the adjusting screw 31 and meshing with an idler gear 34 supportedby the housing 32. A gear 35 is further provided, which in turn mesheswith the idler gear 34 for rotating said gear and is secured to the rearend of a transverse feed shaft 36 which terminates at its forward endinterior- 1 of the bed 15. The forward end of the shaft 36 has securedto it a worm wheel 37 which is adapted to mesh with a worm 38 rotatablymounted in a bracket 39 pivoted at 40 to a fixed part 44 of the bed 15.The bracket 39 has depending from it a lug 41 in which is mounted a stud42 carrying in its forward end a roller 43. J ournaled in the fixed part44 of the bed 15 is a shaft 45 on which is secured a cam 46 in alignmentwith the roller 43 for engaging same. The shaft 45 is operativelyconnected with a manually operating lever 47 mounted on the forward faceof the bed 15 for oscillating the said shaft and consequently the cam 46secured thereto. Actuation of the lever 47 in the proper direction willoscillate the cam 46 in a counterclockwise direction as seen in Fi re 3,WhlCh through its interengagement with the roller 43 oscillates thebracket 39 in a corresponding counterclockwise direction to interengagethe threads of the worm 38 with the teeth of the worm wheel 37. Thisoscillation of the bracket 39 is limited by an adjustable abutment screw48 carried thereby and engaglng with the fixed portion 44 of the bed.The worm 38 is continuously rotated by a motor 49 illustrateddiagrammatically in Figures 12 and 13 so that when the worm and wormwheel 38 and 37 are intermeshed the shaft 36 is being rotated to rotatethe screw 31 and feed the grinding wheel toward the work. Simultaneouslywith the rotation of the shaft 36, there is rotated a drum 5O keyed orotherwise secured thereto, which has secured to it one end of a belt orband 51, the other end of which carries a weight 52. The weight 52 isenclosed within a suitable guide or the like 58. From this it will beseen that as the shaft 36 is rotated in a clockwise direction, for examIe, the band 51 is wound around the drum 5(? so that when the worm 38and worm wheel 37 are disen aged, as seen in Figure 3, the weight 52 wil reversely rotate the shaft 36 and retract the inding wheel carriage.

Referring now to Figure 12, it will be noted that there is shown a pairof main electrical leads 56 and 57 the former or positive leadhavingethe master control switch 58 therein and ing connected throughthe handle 47a, which is the same as the handle 47, and branch lead 59to one end of the motor 49. The remainin or negative lead 57 isconnected to the ot er side of the motor 49 by a branch wire or lead 60.Extending from the branch lead 59 is a wire 61 terminating in onecontact of a magnetic switch 62, the other contact of this switch beingconnected by a wire 63 with one end of a magnet coil. 64, the other endof this coil being in turn connected by a wire 65 with the branchnegative or return lead 60. As shown in Figure 12, this magnetic switch62 is closed, thereby completing an electrical circuit and energizingthe electromagnet 64 which operates on the end of lever 47a to hold itin the position illustrated for maintaining engagement between the worm38 and worm wheel 37. In actual practice, and as shown in Figure 3, theoscillating or pivot shaft 45 is provided with a finger 66 which engageswith the magnet 64 for holding the parts in the position illustrated inFigure 12.

To discontinue the .feed the magnet 64 is de-energized thereby releasingthe lever 47a or fin er 66 so that the worm wheel and worm may hedisengaged to permit retraction of the grinding wheel, which will bedescribed in detail later.

The sizing mechanism here illustrated comprises an electromagneticgenerator indicated structurally in Figures 1, 2, 4 and 6 by thereference character 67 and diagrammatically in Figures 11 and 13 by thereference character 68. The generator 67 or 68 is carried by an arm 69pivoted at 70 to a block 71. The arm 69 has projecting from it on oneside of the pivot 70 a lug 72 against whch abuts one end of a spring 73contained within a socket 74 formed in the block 71. The spring 73 tendsto oscillate the arm 69 in a counterclockwise direction about the pivot70 to actuate the generator 67 toward the operative face of the grindingwheel 29. This movement of the arm 69 is adjustably limited b means of astop screw 75 threaded throug a tongue 76 depending from the block 71.

The block 71 is provided with a dovetailed guideway 77 receiving acorrespondingly shaped guide tongue 78 formed on a swivel plate 79. Theswivel plate 79 is substantially L-shaped, as seen in Figure 6, toprovide the depending arm 80 in which is journaled one end of anadjusting screw 81. The adjusting screw 81 is threadedly received in thetongue 76 of the plate 79 and is further provided on its outer end withan operating knob 82 whereby it may be rotated for effecting adjustmentof the block 71 relative to the plate 79. i The swivel plate 79 hasprojecting from its upper surface a stud 83 rece'ved in an eye 84 formedin one end of an arm 85. The swivel plate 7 9 is secured to the arm 85by means of a nut 86 received on the extreme threaded end of the stud 83and it will be seen that the swivel plate 79 may be adjusted to anydesired point about the axis of the stud 83 for aligning the generator67 with the face of the grinding wheel 29.

The arm 85 is provided in its other end with a second eye 87 throughwhich a T-bolt 88 extends having its T-shaped head 89 received in a slot90 formed longitudinally of a beam 91. The beam 91 is formed integralwith a slide 92 which is provided with a dove-ta'led guideway 93receiving a correspondingly shaped guide tongue 94 formed on the fixedslide 95. The fixed slide 95 is secured in any desirable manner such asby cap screws 96 to the face of the head stock adjacent the grindingwheel. The fixed slide 95 is formed with an internally threaded lug ornut 97 receiving the threaded end of ad- 'usting screw 98. The screw 98is sw'veled 1n a plate 99 secured to one end of the movable slide 92 andis further provided exteriorly of this plate with an actuating knob 100whereby the said screw is rotated.

From the foregoing it will be noted that there has been provided asupport for the siz'ng member or generator whereby the said generatormay be actuated transversely of the grinding face by adjusting the arm85 along the beam 91 and secured thereto by T-bolt 88, or the generatormay be ad usted toward and from the operative face of the grinding wheelby means of the adjusting screw 98 such as when changing the wheel froma worn wheel to a new wheel or vice versa or it may be adjusted towardthe operative face of the grinding wheel by the adjusting screw 81. Thislatter adjustment, of course, is employed for finer adjustments than thescrew 98. Also the arm 69 may be extremely minutely adjusted relative tothe o )erative face of the grinding wheel through t e adjustable stop 75while being actuated about the pivot of its supporting arm by the spring73. It will also be remembered that the swivel plate 79 may be adjustedin a horizontal plane about the axis of the swivel stud 83 projectingtherefrom for thereby aligning the generator 67 with the plane of theoperative face of the grinding wheel.

As is well known, the operative face of a grindin wheel while reasonablysmooth to the tone while traveling at a high grinding rate of speed, isnevertheless composed of an infinite number of cutting edges or pointswith hollows or depressions between the adjacent cutting edges orpoints. Therefore a sensitive member riding on such a surface would tendto ride up and down the sides of the cutting edges causing anoscillatory vibration of the member. Such a member is the armature ofthe generator 67 indicated in the drawings by the reference character101 and carrying at its extreme outer end a diamond or other hardsubstance 102. The armature is shown in Figure 11 as the pivoted arm 103adapted to be oscillated about the pivot 104 for reciprocating the core105 through the coil 106. These parts all constitice may be a magneticpick up or an electromagnetic unit.

The coil 106 has extending from its opposite ends, leads or wires 107and 108, the former being biased as by the battery 109 and terminatingin a ground connection. The line 108 terminates in the rid 110 of avacuum or radio amplifying tu e 111. As usual, this tube 111 includesthe plate 112 upon which is impressed the electrical energy of the grid110 and which plate is connected by wire'or lead 113 to the primary coil114 of a transformer115. The tube 111 is an amplifier tube foramplifying the current generated in the generator 68. The transformer115 has the secondary coil 116 receiving the current from the primary114 and passing same on to the grid 117 of a biased detector tube 118.The bias on the detector tube grid 117 is obtained in the usual mannerby a battery 119. The current in the grid 117 is in turn impressed onthe plate 120 of the tube 118, which plate is connected by a lead orwire 121 to one terminal of a current meter 122, from the other side ofwhich meter extends lead or wire 123. The lead or wire 123 is connectedto one terminal of the B battery 124. This B battery has its other endconnected with the opposite phase terminal of a second B battery 125which is in turn connected through the transformer primary coil 114 withthe plate 112 of the amplifier tube 111.

In order to effect the transferof current from the grids 110 and 117 tothe plates 112 and 120, each of the tubes 111 and 118 is respectivelyprovided with a filament or heating element 126 and 127 having one endthereof connected in series by a wire or lead 128 which terminates atone terminal of the A battery 129. The other terminal of the filaments126 and 127 are likewise connected in series by means of a lead or wire130 termitute the generator 68, which in actual pracnating at the otherterminal of the battery 129.

From the above it will be noted that when the grinding wheel engageswith the diamond or other hard substance 102 it effects a. relativemovement between the core and coil of the generator for generating arelatively weak-current. This current is, however, immediately amplifiedto a oint for operating a current flow meter which would indicate thatthe grinding wheel has approached a definite distance as respects theaxis of the work and that the work has now been reduced to the ultimatedesired size. The amplifier tube 111, detector 118, transformer andparts associated therewith are mounted on a base 195 and enclosed in asuitable housing or cover 196, as shown in Figure 8. This unit may thenbe mounted on the front face of the bed 15.

As shown in Figures 9 and 10, the meter comprises a housing 131 in whichis mounted a dial 132 normally carrying the graduations or indicationsto determine the amount of flow of current in the line. Also mountedwithin the housing 131 is a needle arm 133 carried by a shaft or axle134 and adapted to be oscillated relative to the plate 132 to indicatethe amount of current flow. This needle or arm 133 is deflected in theusual mannenand may be connected by suitable wires or leads extendingfrom the leads 121 and 123.

As shown in Figures 9 and 10, the dial plate 132 is provided with anaperture or opening 135 which is normally closed to prevent lightpassing therethrough by an obstruction or mask 136 carried by the needle133 and adapted to uncover the said aperture when the needle isdeflected.

The meter and its housing 131 are adapted to be enclosed within asuitable casing 137 which includes the base 138 and mounted as a unit onthe forward face of the grinding machine bed as indicated in Figure 1.Within the casing 137 there is also provided a lamp or other source oflight 139 adapted to direct its rays as indicated at 140. in Figure 10,on to the mask 136, which if deflected will pass through the aperture135 to the other end of the casing 137. Mounted in the other end of thecasing 137 is a control mechanism operated by a light sensitive cellindicated by the reference character 141 in Figure 10. This lightsensitive cell energizes or completes an electrical circuit fordisconnecting the feed, as will later appear.

The photoelectric cell 141 is shown diagrammatically in Figure 12, whichdiagrammatically illustrates the electrical circuit controlled andoperated thereby. This circuit includes a suitable transformer 142coupled with a source of current or main power lines 143 and 144 forfeeding current of the desired voltage to the several electricalinstrumentalities here coupled. The coil 145 has feed lines 146 and 147extending therefrom and terminates in a potentiometer 148 which, throughthe line 149 extending from the potentiometer places a negativepotential on the grid 150 of the radio or vacuum tube 151. The vacuumtube 151 includes a plate 152 and filament 153, the latter receiving ourrent from the coil 154 through the lines 155, 147 and 156 to one side ofthe filament and through lines 157, 158 and 159 to the other sidethereof. The late 152 receives current from the coil 160 tlirough theline 161, solenoid 162 and line 163, the current tending to return throuh the filament and line 159 to the upper sife of the coil, but beingblocked by the negative electrical potential on the grid 150. Theintermediate portion of the coil 160 isconnected by a line 164 to oneelement 165 of the light sensitive or photoelectric cell 141 while thesecond element 166 thereof is connected by a line 167 to thepotentiometer grid line 149. The solenoid 162 has extending therethrougha core 168 secured to a bell crank 169 pivoted at 170 for o erating aswitch blade 171. This switch b ade 171 is employed for completing anelectrical circuit including the conductor 172 from the main line 143through a conductor 173.to the second main line 144. This conductor 173has included therein the solenoid 174. A core 175 associated with thesolenoid 174 is employed for operating a switch blade 176 about itspivot 177 to complete a second shu'nt circuit extending from the line173 through a conductor 178 and a second conductor 179 extending from anelectrical contact associated with switch blade 176. i

The branch circuit conduit 172 is connected by a wire or lead 180 withone end of a coil 181 of magnetic switch 182. The other end of this coil181 is connected to the lead 179. The magnetic switch 182 includes thecore 183 which passes through the coil 181 and carries the switch blade184. This blade 184 is normally elevated by means of a spring 185 actingon the end of the core 183 for normally holding the switch 182 in anopen condition. Extending from one contact of the switch 182 is a wireor lead 186 that connects with one end of solenoid switch coil 187 ofthe solenoid switch 62. The other end of this coil is connected by awire or lead 188 to the electric line 59. The other contact of theswitch 182 is connected by the wire or lead 189 with the line 60 of themain motor circuit.

The operation of the mechanism is as follows. When the grinding wheelhas reduced the work to the final desired size, it operates thegenerator 68 for generating a current which is amplified as abovedescribed for actuating the needle arm 133 of the meter 122. The lightsource or lamp being constantl burning is directing its rays on the mask136. Upon deflection of the needle 133 the 152 and from there to thefilament 153 of the vacuum tube 151 to the line 159 and complete anelectrical circuit. Due, however, to the negative electrical otential onthe grid 150 this current flow 1s prohibited. However, upon completionof the electrical circuit through the light sensitive cell 141, thecurrent will flow through the conduit 164 and 167 to the grid 150thereby nullifyin the electrical negative potential thereon anpermitting the flow of the current from the plate 152 to the filament153. This flow of the current energizes the solenoid 162 causing thecore therein to be actuated relative thereto and through the bell cranklever 169 actuates the switch blade 171 and completing an electricalcircuit through the branch conduits which includes the line 173, coil174 and line 172. This in turn operates the switch blade 176 therebycompleting the control circuit which includes the solenoid switch coil181. This circuit, of course, takes in the lead 178 extending from thebranch lead 173, switch blade 176, lead 179. coil 181, lead 180 to thelead 172. 1

The energization of the coil 181 closes the switch 182 against theyielding resistance of the spring 185 thereby completing the electricalcircuit which includes the lead 188, coil 187, of magnetic switch 62,lead 186, switch 182 and lead 189. The energization of the coil 187opens the switch 62 for deenergizing the circuit including theelectromagnet 64. As above described'the magnet 64 normally holds theworm 38 and Worm wheel 37 in operative engagement with one another sothat upon removal of the holding force the worm drops from the wormwheel disconnecting or discontinuing the relative feed and through theweight 52 retracting the grinding wheel from the work.

The modification shown in Figure 13 includes the generator 68 and theelectrical circuit operated thereby, but instead of having the plateline 121 connected with one terminal of. the meter 122, it is connecteddirectly to one end of the magnetic switch coil 181. The other end ofthis coil 181 is connected to one terminal of the battery 124. From thisit will be seen that the electrical circuit may be connecteddirectlywith the control mechanism without passing through theelectrical circuit operated and controlled by1 the light sensitive orphotoelectric cell 14 The modification illustrated in Figure 14 showsthe sizing control mechanism as used with an internal grinder in whichthe work piece 190 is held in a chuck 191 on the end grinding wheel 193secured to the spindle,

or shaft 194. In this construction the generator 67 is positioned toengage the surface of the wheel when it reaches the desired size of thehole.

What is claimed is:

1. In a device of the class described the combination of a tool, asupport for the tool, a work support adjacent the tool, means foractuating the tool and work support toward and from one another, meansfor engaging the tool after it has approached the work a predeterminedamount, said means generating a current upon contact of the worktherewith, and means amplifying said current for discontinuing therelative-feed between the work and tool.

2. In a machine tool of the class described the combination of a bed, agrinding wheel mounted thereon for movement relative thereto, a worksupport carried by the bed for supporting a work piece in the line ofmovement of the grinding wheel, means for effecting the said movement ofthe grinding wheel, and current generating, means carried by the bed inthe line of movement of the grinding wheel adapted to be engaged therebyfor generating a current when the grinding wheel has been actuatedtoward the work a predetermined amount.

3. In a machine tool of the class described the combination of a bed, agrinding wheel mounted thereon for movement relative thereto, a worksupport carried by the bed for supporting a work piece in the line ofmovement of the grinding wheel, means for effecting the said movement ofthe grinding wheel, current generating means carried by the bed in theline of movement of the grinding Wheel adapted to be engaged thereby forgenerating a current when the grinding wheel has been actuated towardthe work a predetermined amount, and means operated by said generatedcurrent for effecting a cessation in the feed of the grinding wheel.

4. In a machine tool of the class described the combination of a bed, agrinding wheel mounted thereon for movement relative thereto, a worksupport carried by the bed for supporting a work piece in the line ofmovement of the grinding wheel, means for effecting the said movement ofthe grinding wheel current generating means carried by the bed in theline of movement of the grindlng wheel adapted to be engaged thereby forgenerating a current when the grinding wheel has been actuated towardthe work a predetermined amount, means operated by said generatedcurrent for effecting a cessation in the feed of the grinding wheel, apivotally mounted arm for supporting the current generator,

means supporting the arm on the bed for adjustment toward the rindingwheel and transversely thereof, and means for locking the arm in itsseveral adjusted positions.

5. In a grinding machine of the class described the combination of awork support and a grinding wheel support, means for effecting arelative feed between the grinding wheel and work, and means forlimiting said relative feed comprising a current generator adapted to beengaged by the rinding wheel, an amplifier for amplifying t e current,and means for effecting the disconnection of the feeding means operatedby the amplified current.

6. In a grinding machine of the class described the combination of abed, a grinding wheel mounted thereon for movement relative thereto, awork support mounted on the bed, means for effecting a relative axialapproach of the grindin wheel and work to effect a stock removal rom thework, means for interrupting said relative approach of the work andgrinding wheel comprising a current generator for generating a currentupon contact of the wheel therewith, a current amplifier for amplifyingthe current to a point for operating a current flow meter, a controlcircuit for discontinuing the relative approach of the work and wheel,and means controlled by the current flow meter for de-energizing thefeed control circuit.

7. In a grinding machine of the class described the combination of abed, a work support mounted on the bed, a grinding wheel mounted on thebed, means including a pair of disengageable members for efl'ecting arelative feed between the worlo support and grinding wheel,electromagnetic means for holding the members in operative engagementwith one another, means for stopping the relative approach between thework and grinding Wheel comprising a current generator adapted to engagethe grinding wheel, and a current amplifier for amplifying the eneratedcurrent to a point for de-energizmg the electro magnetic means.

8. In a grinding machine of the class described the combination of abed, a work support and a tool support carried by the bed, the formersupporting a work piece and the latter supporting a grinding wheel, an

interruptable transmission mechanism for effecting a relative approachof the work support and tool support, means for interrupting thetransmission mechanism includ ing an electrical circuit, a currentgenerator disposed in the path of movement of the work and tool whenactuated toward one another for engagement with one of said members forenerating a current when the said members have reached a definiterelative position, and means operated by said generated current foroperating the control circuit.

9. In a grinding machine of the class described'the combination of abed, a grinding wheel carried thereb a work sup rt on the bed, means fore ectin a relative feed between the grinding whee and work support toeffect a stock removal from a work piece on the work support,electrically controlled means for stopping the relative feed when thework has been reduced to the'desired size, a current generator adaptedto engage the grinding wheel when the work is reduced to the desiredsize for generating a current, an amplifier for amplifying the current,and an o erative connection between the amplifier an electricallycontrolled means for actuating said means by the amplified current.

10. In a grinding machine of the class described the combination of abed, a grinding wheel and work support mounted thereon for movementrelative to one another, a feeding mechanism for effecting said relativemovement, a current generator adapted to engage the grinding wheel whenthe work is reduced to the desired size for generating an electricalcurrent, a current flow meter, an amplifier for amplifying the generatedcurrent to a' point for operating the current flow meter, the currentflow meter having an aperture therethrough, a mask normally sealing saidaperture but deflected upon operation of the current flow meter, andmeans operated by the deflection of the mask for discontinuin therelative feed of the grinding wheel and work,

11. In a grinding machine of the class described the combination of abed, a grinding wheel and work support mounted thereon for movementrelative to one another, a feeding mechanism for effecting said relativemovement, a current generator adapted to engage the grinding wheel whenthe work is reduced to the desired size for generating an electricalcurrent, a current flow meter, an amplifier for amplifying the generatedcurrent to a point for operating the current flow meter, the currentflow meter havin an aperture therethrough, a mask norma ly sealing saidaperture but deflected upon operation of the current flow meter, andmeans operated by the deflection of the mask for discontinuing therelative feed of the grinding wheel and work, said means comprising a liht sensitive cell, a source of light in line wit and adapted to directits rays on the light sensitive cell and I normally interrupted by themask, and an electrical circuit controlled by the light sensitive cell.

12. In a grinding machine the combination of a bed, a grinding wheel anda work support mounted thereon for movement relative to one another, afeed mechanism for effecting the relative movement between the grindingwheel and work support to reduce a work piece carried by the support tothe desired size, means adapted to engage the grinding wheel when thework is reduced to the desired size for generating a current of a givenintensity, a current flow meter, means for amplifying the generatedcurrent to a point for 0 erating the current flow meter, said amp ifyingmeans including a radio vacuum tube, a needle associated with thecurrent flow mete-r and adapted to be deflected upon flow of currenttherethrough, and a light controlled mechanism normally inoperative butrendered operative upon deflection of the needle for discontinuing therelativefeed between the grinding wheel and work.

13. In a grinding machine the combination of a bed, a grinding wheel anda work support mounted thereon for movement relative to one another, afeed mechanism for effecting the relative movement between the grindingwheel and work support to reduce a work piece carried by the support tothe desired size, means adapted to engage the grind ing wheel when thework is reduced to the desired size for generating a current of a givenintensity, a current flow meter, means for amplifying the generatedcurrent to a point for operating the current flow meter, said amplifyingmeans including a radio vacuum tube, a needle associated with thecurrent flow meter and adapted to be deflected upon flow of currenttherethrough, a light controlled mechanism normally inoperative butrendered operative upon deflection of the needle for discontinuing therelative feed between the grinding wheel and work, and means retractingthe wheel and work upon discontinuance of the feed.

14. In a grinding machine the combination of a bed, a grinding wheel anda work support mounted thereon for movement relative to one another, afeed mechanism for effecting the relative movement between the grindingwheel and work support to reduce a work piece carried'by the support tothe'desired size, means adapted to engage the grinding wheel when thework is reduced to the desired s'ze for generating a current of a ivenintensity, a current flow meter, means or amplifying the generatedcurrent to a point for o erating the current flow meter, said ampli yingmeans including a radio vacuum tube, a needle associated with thecurrent flow meter and adapted to be deflected upon flow of cnrrenttherethrough, a light controlled mechanism normally inoperative butrendered o erative upon deflection of the needle for discontinuing therelative feed between the grinding wheel and work, means retracting thewheel and work upon discontinuance of the feed, and means for supportingthe current generator for universal adjustment relative to the operativeface of the grinding wheel.

15. In a sizing control mechanism for use with grinding machines to cutoff the relative feed between a grinding wheel and work piece when thework piece is reduced to the final desired size, the combination of acurrent generator positioned at a point in the path of travel of thewheel representative of the final size of the work and adapted tocontact with the face of the wheel, and means operated by the generatedcurrent for interruptin the feeding mechanism.

16. n a sizing control mechanism for use with rinding machines to cutoff the relative feed tween a grinding wheel and work piece when thework piece is reduced to the final desired size, the combination of acurrent generator positioned at a point in the path of travel of thewheel representative of the final size of the work and adapted tocontact with the face of the wheel, means operated by the generatedcurrent for interrupting the feeding mechanism, a pivotally mounted armsupporting the generator, means supporting the arm for adjustment towardand away from the grinding wheel, means supporting the arm for adustment transversely of the operative face of the wheel, and means forsupporting the arm for oscillatory adjustment to vary the an ularrelationship between the generator an operative face of the wheel. t

17. In a sizing control mechanism for use with grinding machines to cutoff the relative feed between a grinding wheel and work piece when thework piece is reduced to the final desired size, the combination of acurrent generator positioned at a point'in the path of travel of thewheel representative of the final size of the work and adapted to.contact with the face of the wheel, means op-. erated by the generatedcurrent for interrupting the feeding mechanism, a pivotally mounted armsup orting the enerator, means supporting t e arm for a justment towardand away. from the grinding wheel,

-means supporting the arm for ad ustment transversely of the operativeface of the wheel, means for supporting the arm for oscillatoryadjustment to vary the angular relationship between the generator andoperative face of the wheel, and meansfor retracting the grinding whwlfrom the work upon cessation of the feed.

In'testimony whereof, I afiix my signature.

ALFRED G. PLIMMER.

